Let them be themselves! (7)
I believe the answer is:
bygones
'themselves' is the definition.
Both the answer and definition are plural nouns.
Maybe there's an association between them I don't understand?
'let them be' is the wordplay.
I cannot really understand how this works, but
'be' could be 'go' (going is a kind of being) and 'go' is found in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for bygones that I've seen before include "Let ....... be .......; don't hold grudge" , "Things belonging to the past" , "Let these be these to forgive and forget" , "Let - be - means to forget past differences" , "past events" .)